Method of preparation of a patterned decorative material

ABSTRACT

A patterned decorative material is prepared by a method which comprises applying a thermosetting powder coating material to a base plate; melting of the thermosetting powder coating material by heating; simultaneously embossing the coating layer and the base plate while the melted thermosetting powder coating material has a gel fraction formed by a hardening reaction of 0 to 75 weight percent; and further heating to form a hardened coating on the base plate. The patterned decorative material is excellent in appearance, corrosion resistance, weathering resistance and abrasion resistance and is free from the defects of conventional steel plates coated with polyvinyl chloride and the like, such as formation of craze and loss of luster.

This is a division of application Ser. No. 07/464,403 filed Jan. 12,1990, now U.S. Pat. No. 5,051,273.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel method of preparation of apatterned decorative material. In more detail, the invention relates toa method of efficient preparation of a patterned decorative materialhaving embossing on a powder coating layer which has an excellentcorrosion resistance, weathering resistance and abrasion resistance, hasan excellent durability without formation of craze or loss of luster inthe coating even after a prolonged usage and advantageously can beutilized in building materials, electric appliances, furnitures and thelike.

2. Prior Art

For the purpose of giving atmosphere of high grade, patterned decorativematerials excellent in appearance and touch are utilized in buildingmaterials such as wall materials and interior materials of buildings,housing materials of electric appliances, furnitures and the like.

Embossing has been known as one of the methods of preparation of suchpatterned decorative materials. Among such embossed patterned decorativematerials, embossed steel plates are manufactured commercially and areutilized in various applications.

The embossed steel plates are usually prepared by coating and baking alayer of plastisol or organosol made of vinyl chloride resins on a steelplate to form a coated steel sheet and embossing the sheet after thebaking is finished. The thickness of the coating is generally in therange from 300 to 500 micrometer in the case of a plastisol coating andin the range from 70 to 100 micrometers in the case of an organosolcoating (Japanese Patent Publication No. Showa 61-57073).

However, embossed steel plates prepared according to this method have adefect that, because the plastisol or the organosol used for the coatingmaterial contains a large amount of plasticizer such as dioctylphthalate, the coating layer inevitably loses the plasticizer during theprolonged period of utilization and thus formation of craze and loss ofluster are unavoidable.

Another method utilized for a similar purpose is that a coating materialcontaining vinyl chloride resin and a thermoplastic resin is coated tovarying thickness to form a striped pattern by using a roll so that theresulting coating layer has a decorative pattern by the effect of thevariation of thickness (Japanese Patent Publications No. Showa 61-54470and No. Showa 61-54471). However, a thickness in the range from 150 to250 micrometers is required in order to have a decorative patternaccording to this method and productivity is unavoidably decreased.

On the other hand, the method of powder coating is excellent inprocessability, gives a coating excellent in weathering resistance andabrasion resistance, is a typical material-saving process and a typicalnon-hazardous process to the environment and, thus, has been attractinginterest during these years. The method is utilized widely in coatingsof industrial products like outdoor durable structures such as ironframe materials for buildings, guard rails, fences, street lights andgates, steel furnitures, electric appliances and coatings to replaceglass lining.

However, when a coating layer is embossed after the coating layer iscompletely made on the surface of a substrate by applying a powdercoating material on the substrate followed by baking of the coatingmaterial, the coating has problems that craze is formed at the edge ofthe pattern where the thickness of the coating layer varies and thatsome parts of the coating layer are extremely thin so that the coatingis inferior in corrosion resistance during a long period of usage and,as the result, the coating cannot be utilized for a prolonged period.For these reasons, embossed steel plates applied with powder coatingsare actually not utilized for practical purposes.

SUMMARY OF THE INVENTION

The present invention accordingly has an object to provide a method ofpreparation of a patterned decorative material by utilizing an embossingprocess in which thermosetting resins without a plasticizer or the likeare utilized and the material prepared has excellent resistance againstcorrosion, weathering and abrasion and has excellent durability so thatformation of craze or loss of luster does not take place even after aprolonged usage.

One of the methods of preparation of a patterned decorative material ofthe invention comprises application of a thermosetting powder coatingmaterial to a base plate; melting of the thermosetting powder coatingmaterial by heating; simultaneous embossing of the coating layer and thebase plate while the melt thermosetting powder coating material has agel proportion formed by a hardening reaction in the range from 0 to 75weight percent and further heating to form a hardened coating on thebase plate.

Another of the methods of preparation of a patterned decorative materialcomprises application of a thermosetting powder coating material to abase plate; melting of the thermosetting powder coating material byheating; embossing of the coating layer alone while the meltthermosetting powder coating material has a gel proportion formed by ahardening reaction in the range from 15 to 75 weight percent and furtherheating to form a hardened coating on the base plate.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of the coating process line utilized forembossing of both of the coating layer and the base platesimultaneously. FIG. 2 is a schematic diagram of the coating processline utilized for embossing the coating layer alone. FIG. 3 is anexample of the usual chart of differential thermal analysis of athermosetting powder coating material.

Numbers in the figures are: 1; a base plate substrate, 2; a powdercoating machine, 3; a heating furnace, 4(A), 4(B), 4'(A) and 4'(B);embossing rolls, 5; a baking furnace and 6; a coated and embosseddecorative material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods of achieving the object described above were intensivelyinvestigated by the inventors and it was discovered that, because thereare two kinds of embossing processes, namely, simultaneous embossing ofthe coating layer and the base plate and embossing on the coating layeralone leaving the base plate intact, each of the embossing processesmust be conducted under the optimum condition determined for each ofthem.

The inventors discovered, at first, that, when the embossing is madesimultaneously on both of the coating layer and the base plate, thetemperature of melting by heating and the temperature of the hardeningreaction are different, that the coating layer can be kept at a fluidcondition for a certain period of time and that the embossing can beconducted effectively during this period of time.

The inventors further discovered that, when the embossing is made on thecoating layer alone, the condition of hardening must be limited withincertain range rigorously and that a beautifully decorated material canbe prepared if the embossing is made while the gel content of thecoating layer is within certain range.

The invention thus completed to achieve the object is explained indetail in the following.

According to the invention, the embossing is made while the coatinglayer is still in a fluid condition and then the embossed coating layeris baked to form a hardened layer. By applying this process, the defectsfound in the processes in the prior arts such as formation of craze atthe edge of decoration and formation of spots of extremely thin coatingcan be prevented.

As the powder coating material of the invention, all kinds ofthermosetting powder coating material can be utilized as is evident fromthe mechanism of the process of the preparation.

For example, FIG. 3 shows a result of a differential thermal analysis ona conventional thermosetting powder coating material (Metal Finishing,Mar., 1979, page 68). The curvature between A and B in FIG. 3 shows anendothermic process caused by the melting of the resin and the curvaturebetween C and E in the same figure shows an exothermic reaction of theresin and the crosslinking reagent. The coating layer remains fluid inthe condition between B and C and is still remaining fluid in thecondition between C and D even though the reaction already started. Theprocess of embossing can be conducted during the condition between B andD in which the gel content of the coating layer is in the range from 0to 75 percent.

When the rate of increase of temperature during the period describedherein is adjusted depending on the rate of the hardening reaction, theconditions of the process of embossing is adjusted to suit all kinds ofthermosetting powder coating materials.

As the base plate utilized in the invention, a plate having a flat shapeis more suitable because the local accumulation of the resin is moreeasily avoided. However, the shape of the base plate is not limited to aflat shape, but a plate having a curvature can also be utilized.

Examples of the base plate utilized are steel plates such as plates ofthick to medium thickness, thin plates and zinc plated plates, aluminumplates, wooden plates, plywoods, plastic plates and the like and steelplates are preferably utilized. When the embossing is made on both of acoating layer and a base plate, a base plate having no malleability,such as a wooden plate, cannot be utilized.

In the process of embossing of the invention, at first, a powder coatingmaterial which comprises a thermosetting resin as the main component isapplied to the surface of a base plate. However, it is the generallyutilized practice that conditioning of the surface of the base plate ismade prior to the application of the coating material.

The conditioning of the surface of the base plate is made for thepurpose of making the condition of the surface so that the coating layercan adhere to the surface of the base plate tightly and assuming thedurability of the coating layer during a prolonged period. The method ofconditioning is not particularly limitative and any of theconventionally utilized methods can be used depending on the propertiesof the base plate. For example, when a steel plate is utilized as theflat base plate, the methods of the conditioning generally utilized area degreasing treatment, a rust removing treatment, chemical coatingtreatment and the like.

When it is desired, coating of a primer may be applied to the surface ofthe base plate conditioned as described above for the purpose ofincreasing the adhesion of the powder coating layer to the surface.

A coating material which has affinity to both of the base plate and thepowder coating layer is suitable for the primer coating. The primercoating functions as an adhesion mediator between the powder coating andthe base plate and the thickness of the coating layer of 10 micrometeris satisfactory. Generally, the primer coating is dried by baking afterit is applied to the surface.

The powder coating material utilized in the invention is notparticularly limitative so long as it comprises a thermosetting resin asthe main component. Examples of such thermosetting resins are epoxyresins, polyester resins, acrylic resins, fluorohydrocarbon resins andthe like and they are utilized either alone or as a mixture of two ormore kinds.

The crosslinking agents utilized in the invention are, for example,melamine resins, blocked polyisocyanate compounds, urethodionecompounds, triglycidyl isocyanurate (TGIC) compounds which containglycidyl groups or glycidyl groups and hydroxyl groups, polybasic acids,amine compounds, amides and the like and they are utilized either aloneor as a mixture of two or more kinds.

The thermosetting powder coating material of the invention thus preparedcan be compounded with coloring pigments, metal powders, additives andcatalysts according to requirements. Examples of such coloring pigmentsare inorganic pigments such as titanium dioxide, iron oxide, carbonblack and the like, organic pigments such as phthalocyanine blue,phthalocyanine green, quinacridone pigments, isoindolinone pigments andthe like and fillers such as talc, silica, calcium carbonate, bariumsulfate and the like. Examples of such metal powders are aluminumpowder, copper powder and the like. Examples of such additives are micapowder, leveling agents, ultraviolet light absorbents, stabilizersagainst thermal degradation, foam preventing agents and the like.Examples of such catalysts are organotin compounds and the like.

The thermosetting powder coating material of the invention can beprepared according to conventionally practiced methods.

The method of application of the powder coating material of theinvention to the surface of the base plate is not limitative butconventionally practiced methods for the application of a powder coatingmaterial such as flame spray coating, fluidized bed coating,electrostatic spray coating, corona discharge coating, frictionelectrostatic spray coating, electrostatic fluidized bed coating and thelike can be utilized.

The electrostatic spray coating is a preferable method among thesemethods. In the electrostatic spray coating, powders of the coatingmaterial are negatively charged by passage through a nozzle of a spraygun which is impressed with a high voltage of more than -70,000 volts,sprayed to an earthed substrate and attached to the surface of thesubstrate by electrostatic force.

In the method of the invention, the base plate, the surface of which isconditioned and, if desired, coated with a primer, is preheated to 50°to 80° C. if necessary and the thermosetting resin powder coatingmaterial is applied to the surface by utilizing one of the methodsdescribed above. The thickness of the coating layer is generallyselected to be in the range from 30 to 200 micrometers.

The coated plate is heated to a temperature above the melting point ofthe powder coating material so that the coating material melts and isembossed by using rolls or presses while the coating material maintainsits fluidity. It is an advantageous practice that the rolls or thepresses utilized are cooled with water or coated with anfluorohydrocarbon resin so that the powder coating material does notadhere to the roll or the press while it is still fluid. Examples of thefluorohydrocarbon resins advantageously utilized are resins having ahigh degree of anti-adhesiveness such as tetrafluoroethylene resins,trifluoroethylene resins and the like.

When the embossing is made on both of the coating layer and the baseplate simultaneously according to the method of the invention, theembossing is made before the completion of the hardening while the gelproportion of the coating layer is in the range from 0 to 75 weightpercent, preferably in the range from 0 to 60 weight percent, and thehardening reaction is completed after the embossing is done. Byutilizing this method, strain is not left remaining in the material andthe formation of craze is avoided. When the gel proportion of thecoating layer is more than 75 percent, craze is formed at embossedportions and the quality of the product is bad.

When the embossing is made on the coating layer alone according to theother method of the invention, it is required that the embossing is madeduring the process of hardening when the gel proportion of the coatinglayer is in the range from 15 to 75 weight percent, preferably in therange from 25 to 60 weight percent.

When the gel proportion is less than 15 weight percent, the shape of thepatterned decoration is deformed by heat after the embossing iscompleted and the patterned decoration cannot be obtained as accuratelyas it is designed. When the gel proportion is more than 75 weightpercent, the powder coating layer acquires rubbery elasticity and thevariation in the thickness is not formed as it is designed, resulting inbad appearance of the coating layer.

The gel proportion described in the invention is obtained by thefollowing method: a portion of the coating layer is taken as a sample;the sample is extracted with tetrahydrofuran for 5 hours under reflux;the residue of the extraction is dried; and the weight fraction of theresidue against the total sample is calculated.

In the practice of the invention, it is desirable that the change of thegel proportion depending on the pattern of heating during thepreparation process is measured by experiments in advance and the mostsuitable gel fraction is selected by selecting a suitable time ofheating according to the data thus obtained.

In the method of the preparation of the invention, the embossed materialis baked in a baking furnace at the temperature in the range from 150°to 250° C. for the time in the range from 1 to 30 minutes to completethe hardening reaction.

Thus, the embossed pattern can be completed without formation of astrain caused by the process.

The method of the preparation of the invention can be conductedcontinuously while all of the processes are made by transferringmaterials on a conveyer belt continuously.

In the following, examples of favorable practices of the methods of theinvention are given to illustrate the methods of the invention in moredetail with reference to the attached drawings.

EXAMPLE 1

FIG. 1 shows the process of embossing when both of the powder coatinglayer and the base plate are embossed simultaneously.

The process shown in FIG. 1 is an example of the favorably practicedcoating line of the invention. The substrate, 1, is a flat plate whichis treated in the processes I through IV.

In the process I, a steel plate which has been treated with a degreasingprocess, a rust removing process and a chemical coating process inadvance is used as a base plate. A polyester powder coating material issprayed on the surface of the steel plate to form a coating layer ofthickness of about 50 micrometer by electrostatic spray coating methodusing spraying machine GX-108 manufactured by Onoda Cement Co., Ltd.

In the process II, the steel plate with the coating layer is heated to200° C. for 2 minutes by passing the plate through a heating furnace, 3,and the powder coating material is made fluid by melting.

In the process III, the steel plate with the coating layer is passedthrough embossing rolls, 4(A) and 4(B), and embossing is made on both ofthe powder coating layer and the steel base plate as shown by 6.

In the process IV, the embossed plate is passed through a bakingfurnace, 5, of temperature of 250° C. in 5 minutes, the hardeningreaction of the coating layer is completed and the embossed steel plate,6, is prepared.

The embossed steel plate thus prepared had a beautiful appearance andshowed no craze at all.

During the process of the embossing, a portion of the coating layer atthe edge of the plate is taken as a sample at the moment when theportion passes through the embossing roll and gel proportion is measuredwith the sample. In Table 1 are shown the kind of coating materialutilized, conditions for the process II, gel proportion measured,conditions for the process IV and appearance of the plate prepared.

EXAMPLES 2 THROUGH 7 AND COMPARATIVE EXAMPLES 1 THROUGH 3

A steel base plate and a coating layer on the surface of the steel plateare embossed simultaneously by the same process as that of Example 1except that different kinds of coating material, different conditionsfor the process II and different conditions for the process IV areemployed. In Table 1 are shown the kind of coating material utilized,conditions for the process II, gel fraction measured, conditions for theprocess IV and appearance of the plate prepared.

                                      TABLE 1 (Part 1)                            __________________________________________________________________________                        Example                                                                       1    2    3    4    5                                     Thermosetting       Konac                                                                              Konac                                                                              Konac                                                                              Konac                                                                              Konac                                 powder coating      No. 1600                                                                           No. 2500                                                                           No. 3700                                                                           No. 4600                                                                           No. 4600                              material            White 1)                                                                           White 2)                                                                           White 3)                                                                           White 4)                                                                           White 4)                              __________________________________________________________________________    Heating   Temperature (°C.)                                                                200  200  200  200  200                                   condition Time (min.)                                                                             2    1    1    1    2                                     Gel proportion (%)                                                                      5)        30   26   63   41   64                                    Hardening Temperature (°C.)                                                                250  250  250  250  250                                   condition Time (min.)                                                                             5    5    3    3    3                                     Appearance of                                                                           6)        good good good good good                                  the coating                                                                   __________________________________________________________________________     1) Trade name of a polyester resin powder coating material manufactured b     Nippon Yushi Co., Ltd. (A polyurethane type material in which a polyester     resin is used as the resin component and a blocked isocyanate compound is     used as the crosslinking agent)                                               2) Trade name of an epoxy/polyester resin powder coating material             manufactured by Nippon Yushi Co., Ltd. (A hybrid type material in which a     epoxy resin and a polyester resin are used)                                   3) Trade name of an epoxy/polyester resin powder coating material             manufactured by Nippon Yushi Co., Ltd. (A material in which an epoxy          compound is used as the resin component and an amine compound is used as      the crosslinking agent)                                                       4) Trade name of an acrylic resin powder coating material manufactured by     Nippon Yushi Co., Ltd. (A material in which an acrylic resin is used as       the resin component and a dibasic acid is used as the crosslinking agent)     5) Measured on a sample of the coating layer according to the following       equation after the sample is refluxed with tetrahydrofuran for 5 hours        followed by drying in vacuo at 50° C. for 5 hours: gel proportion      (weight after the treatment/original weight) × 100                      6) good: the coating layer has a distinct pattern by variation of the         thickness and no crazing is found. bad: the coating has a pattern by          variation of the thickness but crazing is found.                         

                                      TABLE 1 (Part 2)                            __________________________________________________________________________                        Example   Comparative Example                                                 6    7    1    2    3                                     Thermosetting       Konac                                                                              Konac                                                                              Konac                                                                              Konac                                                                              Konac                                 powder coating      No. 4600                                                                           No. 9000                                                                           No. 1600                                                                           No. 4600                                                                           No. 4600                              material            Clear 7)                                                                           White 8)                                                                           White 1)                                                                           White 4)                                                                           Clear 7)                              __________________________________________________________________________    Heating   Temperature (°C.)                                                                200  200  230  230  230                                   condition Time (min.)                                                                             1    2    4    4    4                                     Gel proportion (%)                                                                      5)        39   52   78   88   83                                    Hardening Temperature (°C.)                                                                250  250  250  250  250                                   condition Time (min.)                                                                             3    3    5    3    3                                     Appearance of                                                                           6)        good good bad  bad  bad                                   the coating                                                                   __________________________________________________________________________     1), 4), 5) and 6) are shown in Part 1 of the table.                           7) Trade name of an acrylic resin powder coating material manufactured by     Nippon Yushi Co., Ltd. (A material in which an acrylic resin is used as       the resin component and a dibasic acid is used as the crosslinking agent)     8) Trade name of a polyester resin powder coating material manufactured b     Nippon Yushi Co., Ltd. (A TGIC type material in which a polyester resin i     used as the resin component and TGIC is used as the crosslinking agent)  

EXAMPLE 8

FIG. 2 shows the process of embossing when the powder coating layeralone is embossed.

The process shown in FIG. 2 is an example of the favorably practicedcoating line of the invention. The substrate, 1, is a flat plate whichis treated in the processes I through IV.

In the process I, a steel plate which has been treated with a degreasingprocess, a rust removing process and a chemical coating process inadvance is used as a base plate. A polyester powder coating material issprayed on the surface of the steel plate to form a coating layer ofthickness of about 50 micrometer by electrostatic spray coating methodusing spraying machine GX-108 manufactured by Onoda Cement Co., Ltd.

In the process II, the steel plate with the coating layer is heated to200° C. for 2 minutes by passing through a heating furnace, 3, and thepowder coating material is made fluid by melting.

In the process III, the steel plate with the coating layer is passedthrough embossing rolls, 4'(A) and 4'(B), and embossing is made on thepowder coating layer alone as shown by 6.

The embossing rolls utilized for the embossing of the coating layercomprise two kinds of rolls. One of them, 4'(A), is located on the upperside of the plate and equipped with a pattern for the embossing. Theother roll, 4'(B), is located on the lower side of the plate and thesurface is plain without a pattern.

In the process IV, the embossed plate is passed through a bakingfurnace, 5, of temperature of 250° C. in 5 minutes, the hardeningreaction of the coating layer is completed and the steel plate embossedon the coating layer alone, 6, is prepared.

The embossed steel plate thus prepared had a pattern with variedthickness, a beautiful appearance and showed no craze at all.

During the process of the embossing, a portion of the coating layer atthe edge of the plate is taken as a sample at the moment when theportion passes through the embossing roll and gel proportion is measuredwith the sample. In Table 2 are shown the kind of coating materialutilized, conditions for the process II, gel proportion measured,conditions for the process IV and appearance of the plate prepared.

                                      TABLE 2 (Part 1)                            __________________________________________________________________________                        Example                                                                       8    9    10   11   12   13                               Thermosetting       Konac                                                                              Konac                                                                              Konac                                                                              Konac                                                                              Konac                                                                              Konac                            powder coating      No. 1600                                                                           No. 2500                                                                           No. 3700                                                                           No. 4600                                                                           No. 9000                                                                           No. 9000                         material            White 2)                                                                           White 2)                                                                           White 2)                                                                           White 2)                                                                           White 2)                                                                           Clear 2)                         __________________________________________________________________________    Heating   Temperature (°C.)                                                                200  200  200  200  200  200                              condition Time (min.)                                                                             2    2    1    1    1    2                                Gel proportion (%)  30   38   63   41   32   59                               Hardening Temperature (°C.)                                                                250  250  250  250  250  250                              condition Time (min.)                                                                             5    5    3    3    5    5                                Appearance of                                                                           1)        good good good good good good                             the coating                                                                   __________________________________________________________________________     1) good: the coating layer has a pattern by variation of the thickness        bad: the coating layer does not have a pattern by variation of the            thickness                                                                     2) Trade names of the powder coating materials are the same as those in       Table 1.                                                                 

                                      TABLE 2 (Part 2)                            __________________________________________________________________________                        Comparative example                                                           4    5    6    7    8    9                                Thermosetting       Konac                                                                              Konac                                                                              Konac                                                                              Konac                                                                              Konac                                                                              Konac                            powder coating      No. 1600                                                                           No. 1600                                                                           No. 4600                                                                           No. 4600                                                                           No. 9000                                                                           No. 9000                         material            White 2)                                                                           White 2)                                                                           White 2)                                                                           White 2)                                                                           White 2)                                                                           Clear 2)                         __________________________________________________________________________    Heating   Temperature (°C.)                                                                180  230  180  230  180  230                              condition Time (min.)                                                                             2    4    1    4    1    4                                Gel proportion (%)  5    78   8    88   7    85                               Hardening Temperature (°C.)                                                                250  250  250  250  250  250                              condition Time (min.)                                                                             5    5    3    3    5    5                                Appearance of                                                                           1)        bad  bad  bad  bad  bad  bad                              the coating                                                                   __________________________________________________________________________     1) and 2) are shown in Part 1 of the table.                              

EXAMPLES 9 THROUGH 13 AND COMPARATIVE EXAMPLES 4 THROUGH 9

A coating layer alone on a steel plate is embossed by the same processas that of Example 8 except that different kinds of coating material,different conditions for the process II and different conditions for theprocess IV are employed. In Table 2 are shown the kind of coatingmaterial utilized, conditions for the process II, gel fraction measured,conditions for the process IV and appearance of the plate prepared.

To summarize the advantages obtained by the invention, the patterneddecorative material prepared by the method of the invention whichcomprises embossing of a powder coating on a steel plate in a specifiedcondition is excellent in appearance, corrosion resistance andweathering resistance and free from the defects of conventional steelplates coated with polyvinyl chloride and the like such as formation ofcraze and loss of luster.

The patterned decorative material prepared according to the method ofthe invention is favorably utilized as building materials such as wallmaterials and interior materials of buildings, housing materials ofelectric appliances, furniture materials and the like.

What is claimed is:
 1. A method of preparation of a patterned decorativematerial which comprises applying a thermosetting powder coatingmaterial comprising a hardener to a base plate, melting thethermosetting powder coating material by heating, simultaneouslyembossing the coating layer and the base plate while the meltedthermosetting powder coating material has a gel proportion formed by ahardening reaction from 0 to 75 weight percent and further heating toform a hardened coating on the base plate.
 2. The method according toclaim 1, wherein the embossing is carried out while the meltedthermosetting powder coating material has a gel proportion formed by ahardening reaction from 0 to 60 weight percent.
 3. The method accordingto claim 1, wherein the thermosetting powder coating material isselected from the group consisting of polyester powder coating material,epoxy powder coating material, acryl powder coating material andfluorohydrocarbon resin powder coating material.
 4. The method accordingto claim 1, wherein the base plate is selected from the group consistingof a steel plate, a zinc plated plate, an aluminum plate, a wooden plateand a plastic plate.
 5. The method according to claim 1, wherein thecoating layer has a thickness of 30 to 200 micrometers.
 6. The methodaccording to claim 1, wherein the hardener is a crosslinking agentselected from the group consisting of melamine resins, blockedpolyisocyanate compounds, urethodione compounds, triglycidylisocyanurate compounds which comprise glycidyl groups or glycidyl groupsand hydroxyl groups, polybasic acids, amine compounds, amides andmixtures thereof.
 7. The method according to claim 1, wherein the powdercoating is applied to the base plate by a method selected from the groupconsisting of flame spray coating, fluidized bed coating, electrostaticspray coating and corona discharge coating.
 8. The method according toclaim 1, wherein the powder coating is applied to the base plate by amethod selected from the group consisting of friction electrostaticspray coating and electrostatic fluidized bed coating.
 9. The methodaccording to claim 1, wherein the hardening reaction is carried at atemperature of 150° to 250° C. for 1 to 30 minutes.
 10. The methodaccording to claim 3, wherein the base plate is selected from the groupconsisting of a steel plate, a zinc plated plate, an aluminum plate, awooden plate and a plastic plate; the coating layer has a thickness of30 to 200 micrometers; the hardener is a crosslinking agent selectedfrom the group consisting of melamine resins, blocked polyisocyanatecompounds, urethodione compounds, triglycidyl isocyanurate compoundswhich comprise glycidyl groups or glycidyl groups and hydroxyl grouppolybasic acids, amine compound amides and mixtures thereof; the powdercoating is applied to the base plate by a method selected from the groupconsisting of flame spray coating, fluidized bed coating, electrostaticspray coating and corona discharge coating and the hardening reaction iscarried at a temperature of 150° to 250° C. for 1 to 30 minutes.